The closest prior art in this field is provided by Document EP-A-0 327 470.
That document describes the rotor of a rotary electrical machine having permanent magnets of the flux-concentrating type in which the rotor includes a sleeve of non-magnetic material having the drive shaft passing therethrough and fixed to the drive shaft, with fixing being achieved by knurling on the drive shaft co-operating with the surface of the sleeve of non-magnetic material which is a force-fit on the drive shaft.
With a structure of this type, the sleeve is subjected to stresses that exceed the elastic limits of the usable non-magnetic materials. As a result, after a short period of time, play arises that may lead to the motor being damaged. This phenomenon is accentuated by high speeds, such that the prior art motor is unsuitable for operation at such speeds. Further, the differences between the expansion coefficients of non-magnetic and magnetic materials gives rise to unacceptable positive assembly clearances due to the inevitable heating of the motor in operation.
An object of the present invention is to provide a motor in which the rotor avoids the above-mentioned drawbacks.
Another object is to provide a motor of modular type so as to make it possible to build up motors with powers extending over a large range by assembling together a greater or lesser number of the same mechanical components.
Another object of the invention is to provide a motor which is optimized electromagnetically while still retaining a high degree of robustness, in particular at high speeds.